This invention relates to augmenters, and more particularly, to augmenter igniters.
Augmenters are used in gas turbine engines to increase thrust as needed in a flight envelope. An igniter is typically located circumferentially near a bottom of the augmenter. The ignitor typically includes an igniter mounting assembly and an igniter lead extending from an ignition box to an igniter tip. The igniter tip provides an ignition source for the augmenter.
An igniter mounting assembly secures the igniter to the augmenter. Typically the mounting assembly includes an igniter housing secured to the augmenter with a plurality of fasteners. The igniter housing includes an opening at both ends which permits the igniter to extend therethrough to the augmenter. The igniter is installed such that the igniter tip extends into the augmenter a pre-determined immersion depth.
When a gas turbine engine is operating, fuel and air flow through the augmenter at a high temperature and velocity. The high temperatures of the fuel and air subject the augmenter and its associated components to thermal stresses and thermal growths. Such thermal growths often force the igniter radially inward into an ignition zone area which increases the igniter tip temperature and decreases the igniter tip life. As a result, the igniter tip is continually mis-aligned which may decrease the overall performance of the associated gas turbine engine. To correct such igniter tip misalignments, typically a floating ferrule arrangement is included at an interface between the igniter tip and the ignition zone.
In an effort to prevent the thermal growth from having an adverse effect on the igniter, a bulky and adjustable igniter mounting assembly is used. Such an assembly includes a plurality of components fastened tightly together to prevent any single component from thermally expanding independently of any other component. As a result, the components thermally expand causing misalignments and improper immersion depths. Additionally, the bulky floating ferrule assembly extends outward from the augmenter ignition zone and blocks cooling air flow used to cool other gas turbine engine components. Furthermore, because the components are fastened together, although the igniter tip remains in proper alignment with respect to the mounting assembly, it may not remain at a proper immersion depth or at a proper alignment with respect to the augmenter. As a result, overall gas turbine light off performance is decreased.
In an exemplary embodiment, an augmenter includes an igniter mounting assembly which maintains an igniter tip at a proper immersion depth. The igniter includes an igniter lead and an igniter housing assembly. The igniter lead extends from an ignition box and terminates in an igniter tip. The housing assembly is secured to an augmenter with a pair of fasteners and the igniter is secured within the housing assembly with a self-locking nut.
The igniter and igniter housing also include a biasing mechanism coupled between the igniter and the igniter housing. The biasing mechanism biases the igniter against the augmenter to ensure that the igniter tip is maintained at a proper immersion depth within an augmenter ignition zone during gas turbine engine operation. Additionally, the igniter includes an alignment support boss sized to be received in a chamfered opening disposed within the augmenter. The combination of the alignment support boss and the chamfered opening automatically aligns the igniter tip for proper operation when the igniter is fully attached to the augmenter. Furthermore, as the gas turbine engine is operated, the biasing mechanism maintains the igniter tip at a proper immersion depth within the augmenter. In addition, since the igniter is secured within the igniter housing with only a self-locking nut, igniter maintenance efforts are streamlined.